Mugearite
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Fact sheet
Description: 

This fine-grained volcanic rock has a similar composition to basalt, but the oligoclase composition plagioclase feldspar and presence of orthoclase, a potassium rich feldspar, mark it as unusual. The sample comes from a suite of Lower Carboniferous alkaline volcanic rocks in the Scottish Borders, similar in age and composition to others in the Midland Valley of Scotland further north. This sample is from Mellerstain Hill quarry, near Kelso.

In thin section the rock contains olivine phenocrysts altered to chlorite and clay minerals along cracks, grey-pink pyroxene phenocrysts, small orthoclase feldspar phenocrysts and compositionally zoned plagioclase, and some phenocrysts showing almost sieve-like resorption textures. The groundmass comprises plagioclase, pyroxene, olivine and iron oxides.

In Place
In Time
infoImage: 
Location description: 
The Mellerstain Hill quarry, near Kelso, Berwickshire
Accuracy:
Location precision: 
Good
Timescale:
Timescale: 
Carboniferous
Ma = Millions of years ago
In Focus
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Type:
Type: 
igneous
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